June 13, 2022

Disadvantages of Ground Source Heat Pumps

Disadvantages of Ground Source Heat Pumps

What is a ground source heat pump?

Originating in the 19th century by a scientist and engineer duo, ground source heat pumps (sometimes called geothermal heat pumps), have evolved to become one of the most efficient types of renewable energy technology for domestic and commercial use today.

Basically, a ground source heat pump (GSHP) works  by exchanging and utilising heat that’s naturally stored underground closer to the earth’s core. This natural source is known as geothermal heat and regardless of the weather, the temperature deeper within the earth remains consistent.

In fact, around 7m down, the ground stay roughly at the average yearly temperature of the location on the planet.  Here in the UK, that translates to between 7 and 12 ºC.

Of course, 7-12 degrees is still a little bit chilly for heating up our homes in the UK winters. A ground source heat pump is able to collect and utilise this heat using clever compression and vaporisation techniques, which we explain in a bit more detail below.

Once the geothermal heat is collected and transferred by the GSHP to the home or building, it distributes it around the home via existing radiators or through underfloor heating, keeping it toasty and warm all through cold seasons.

During summer, ground source heat pumps are even able to reverse their role as heating system and instead, absorb heat from the home. This heat is carried back into the ground and the building is kept cooler.

Just like air source heat pumps, ground source heat pumps can essentially double up as an air conditioning unit. And just like an air heat pump, both running costs and carbon emissions are dramatically reduced.

The three key parts to a ground source heat pump include the ground heat exchange loop, a heat pump and a heat distribution system.

To the homeowner however, a domestic ground source heat pump simply looks pretty much like an upright freezer.

The heat distribution unit is placed discreetly within the home, complete with temperature controls much like a ‘normal’ heating system.

Once installed, a ground source heat pumps maintenance is minimal, with just a yearly check up from an engineer. Factor in their 25 year life span and the huge reduction in energy bills, ground source heat pump advantages become abundantly clear.  

In terms of efficiency, it’s impressive and another of the biggest ground source heat pump advantages.

For every single unit of electricity that a ground source heat pump uses, four units of heat is generated.

That means that a properly installed GSHP is up to 400% more efficient than its electrical or traditional equivalent. It also means that 70% less carbon dioxide is produced than for a gas heating system.

As it produces no greenhouse gas emissions (another major advantage of a ground source heat pump), having a GSHP is a clean way to produce energy for domestic properties.

If the electricity used to run the heat pump is sourced renewably as well (like from solar panels for instance), the entire heating system can be net zero.  

How does a ground source heat pump work?

So how do ground source heat pumps work?

With the ability to install in any property, ground source heat pumps are an ingenious piece of renewable technology, with physics at the core.

Ground source heat pump systems work on the premise that underground temperatures are warmer than the air in the winter and cooler than the air in the summer. The difference between those ground / air temperatures is what’s then used to transfer heat (or cooling) for the home.

Ground source heating systems work using the three components mentioned above, which work together in a coordinated and efficient way collecting, moving and distributing the heat. The way the heat is collected is from pipes that are laid in one of two ways.

For those with larger gardens, you’ll have horizontal pipelines laid called ‘open loops’.

A ground loop is a long length of specialist piping that’s laid horizontally about 1-2m under the soil around your property.

Typically, the horizontal loop is the preference in the UK because it’s less costly. A disadvantage here is that it does require a lot of space. Because this type of loop must be spaced 1m apart and lay in a straight line, you’ll usually need around triple the amount of floor space you’ll expect to heat.

That said, different types of piping might allow for bends in the configuration and could enhance performance by increasing the amount of heat absorbed.

Much of how much space you need depends on how much heat you need for the size and age of the property, its whereabouts and the ground source heat pump capacity.

Pipes can even be laid beneath water sources to extract heat from water, such as a lake or pond.

For homes short on space, you can drill a deep vertical hole around 100m downwards into the earth. These holes are called ground source heat pumps boreholes and are generally no bigger than a manhole. You may require more than one.

Whether horizontal or vertical ground source heat pump piping, the method of abstraction works much in the same way.

Once up and running, an antifreeze type fluid is circulated through the open loops, which the sucks heat through from the soil and into a heat exchanger.

An evaporator uses this heat to boil the refrigerant at -10 degrees Celsius, turning it into a vapour which can then be used by a compressor.

Once compressed, the vapour decreases in volume but increases in temperature.

This newly converted hot gas is then pushed through the heat pump and into the heat distributor.

During this process the hot gas is converted again by the central heating systems cold water, which condenses the refrigerant back to a liquid.  

Finally, the pressure of the condensed liquid reduces thanks to an expansion valve and completes the circuit – emission free.

How ground source heat pumps work is pretty complex, but what’s impressive is that no external fans or visible equipment is needed. Understandably, ground source heat pump price reflects the complexity of this impressive piece of kit.

The size of a ground source heat pump

Ultimately, the size of heat pump you end up with will largely depend on the size and type of your home, how much energy you consume and what the land around your house is like.

For example, if you have a lot of rock in your surrounding garden, this affects both the layout and the cost.

For a guesstimate of how much space you’ll need to lay horizontal loop systems, you should multiply the square foot of the house by three times.

Vertical ground source systems definitely save space, but will need several boreholes spaced out by 27 feet (8.2m) between each one.

Ground source heat pump grant

Ground source heat pump grants are what makes them more affordable for the average homeowner, whilst the government gets a shot at reaching their net zero ambition for 2050.

With ageing houses across the UK needing a serious energy upgrade, the government put the renewable heat incentive in place. The intention is clearly to help homeowners make the decision to switch to green energy by removing the cost barriers.  

Indeed, over time, the Renewable Heat Incentive (RHI) does bring the cost of ground source heat pump back in line with the more conventional heating systems. However, it does take some years to recoup the initial investment.

Whilst the upfront costs of a ground source heat pump do inarguably cost more, eventual savings via reduced energy bills and the repayment scheme of the ground source heat pump RHI do make it worthwhile in the end.

The renewable heat incentive and ground source heat pumps

Governing body Ofgem pays the homeowner up to 21.29 pence per kWh of energy generated each quarter, for up to seven years after a ground source heat pump has been installed.

The amount of heat that your GSHP produces get estimated according to the energy demands of your property and the efficiency of the actual unit installed, which determines the rating of your Energy Performance Certificate (EPC).

The scheme was originally set up in April 2014 and is due to expire in March 2022. After that, it’s expected that a replacement will step in, but as yet nothing solid has been published.

There are some restrictions in place which set a limit on how much the renewable heat incentive pays out.

With a ground source heat pump, the maximum amount the RHI will pay back is for 30,000 kWh, allowing repayments of £4,258 each year. Over seven years this amounts to £29,806.

So you can see that the outlay costs are all but covered through the repayment scheme.

You can see and compare all the domestic tariffs from Ofgem on their latest domestic RHI tariff table.    

  • In Scotland, local authorities provide interest free loans of up to £10,000 to install a heat pump in their property. This essentially brings the cost down to the same as a gas boiler, except your home heating method will incur cheaper bills AND you’ll be dramatically reducing your carbon footprint.
  • Commercial properties can also enjoy the Renewable Heat Incentive, in that payments are made over an even longer period of time – 20 years in fact.
  • Back in England, you may be able to instigate an Assignment of Rights (AoR), which is where you invite a private investor to pay for the setup of your heat pump. That investor can then legitimately claim the Renewable Heat Incentive payments back themselves.

For those living in flats or apartments, it’s also possible to install a communal heat pump for the entire building, which of course would reduce the cost for everyone.

For the lifetime savings on energy, along with reliability and efficiency, there’s no doubt that ground source heat pumps are a great investment.  

Even without the Renewable Heat Incentive, you’d still get your payment on a GSHP installation eventually, although it would take significantly longer as shown in the table below.

Ground source heat pumps disadvantages

So on to the juice. What are the disadvantages of ground source heat pumps?

Ground source heat pump price

Well for a start, we’d be lying if we didn’t list the ground source heat pump cost as one of the biggest complaints about GSHPs.

We totally appreciate that not everyone has a spare £20,000 lying around (or more if you consider the ground source heat pump borehole cost), even if you do get ground source heat pump costs back (and then some) over the next 7 years through the RHI.  

Ground source heat pump installation

Ground source heat pump installation is another potential drawback. Ground source heat pump installers don’t mean to basically wreck your garden, but they kind of have to. Whether you need horizontal ground source loops or vertical bore holes, it’s going to get messy.

Of course, once it’s in, ground source heating is extremely low maintenance and can be left for literally decades without interference. Which means, you get your garden back.

Water consumption

Water consumption is another less than great feature of your GSHP, particularly for the open loop system, which needs large amounts to continue pumping the heat along.

Distance efficiency

If ground source heat pumps are a large distance away from the property, energy can be lost along the way. Having professional and proper installation of ground source heat pumps is vital to maximise both the efficiency and the savings.

That said, compared to a traditional boiler whose efficiency stands at between 60-90% efficient thanks to the limitations of their design, a ground source heat pumps efficiency basically smashes it out of the park at a 300-500% exchange.

A ground source heat pump is really most appropriate for the average sized home, rather than a huge building or a single apartment. That said, there are always work arounds for larger buildings depending on the energy requirements.

Ground source heat pump advantages

The fact of the matter is, if you do take the ground source heat pump grant into account and can afford the initial outlay, the overall ground source heat pumps reviews are beyond good. Despite the costs, ground source heat pumps still work out cheaper than electric systems.

Homeowners are reporting that they have:

  • Reached a net zero or low carbon level home (depending on whether they’ve installed solar panels and battery storage)
  • All year round low energy bills
  • Complete energy systems for hot and cold weather, eliminating the need for air con or gas boilers
  • Longevity and reliability in their heating system with low maintenance
  • Full convenience as their GSHP is self-regulating and fully automated
  • Space saving as the majority of the system is tucked away underground and there are no fuel storage needs
  • With no fuel delivery, there’s also complete assurance your fuel is at hand at all times underground
  • Completely safe with no risk of inhaling dangerous gasses or combustion
  • Have pollution free air surrounding their property
  • Have a silent system that is out of sight and out of mind
  • Increased property value

If you’re thinking about installing a ground source heat pump system, why not reach out to our professional and experienced renewable heating experts?

BioSun Energy are fully MCS certified and members of the RECC Consumer Code meaning we are fully equipped to provide comprehensive and reliable systems and are bound to deliver the very highest standards in service.

We offer no obligation quotes that are designed to ultimately help homeowners save money with the best ground source heating cost available.

Let's talk about your project

If you have a project in mind or are thinking of installing renewable energy, please contact us for an initial informal chat.